HR: 17:40h
AN: B24A-07    [Abstracts]
TI: Six year carbon budget of a northern peatland: no evidence for substantive increase in DOC loss due to `biogeochemical drought'
AU: * Roulet, N T
EM: nigel.roulet@mcgill.ca
AF: McGill School of Environment & Department of Geography, McGill University 3534 University Avenue, Montreal, QC H3A 2A7 Canada
AU: Lafleur, P M
EM: plafleur@trentu.ca
AF: Department of Geography, Trent University 1600 Westbank Drive, Peterborough, ON K9J 7B8 Canada
AU: Moore, T R
EM: tim.moore@mcgill.ca
AF: Departmnet of Geography, McGill University 805 Sherbrooke St. W., Montreal, QC H3A 2K6 Canada
AU: Admiral, S
EM: sadmiral@trentu.ca
AF: Department of Geography, Trent University 1600 Westbank Drive, Peterborough, ON K9J 7B8 Canada
AU: Dalva, M
EM: dalva@geog.mcgill.ca
AF: Departmnet of Geography, McGill University 805 Sherbrooke St. W., Montreal, QC H3A 2K6 Canada
AU: Fraser, C
AF: Departmnet of Geography, McGill University 805 Sherbrooke St. W., Montreal, QC H3A 2K6 Canada
AU: Humpherys, E
EM: elynhumphreys@trentu.ca
AF: Department of Geography, Trent University 1600 Westbank Drive, Peterborough, ON K9J 7B8 Canada
AU: Rattle, J
EM: jmrattle@yahoo.ca
AF: Departmnet of Geography, McGill University 805 Sherbrooke St. W., Montreal, QC H3A 2K6 Canada
AB: Northern peatlands store between 250 and 500 Gt C, or 10 to 20% of all terrestrial carbon. Accumulation of peat, which comprises partially decomposed dead plant material, results from plant production persistently exceeding decomposition. Decomposition is inhibited by the presence of saturated conditions. Since the hydrology of peatlands is in part of function of their climatic setting (precipitation and temperature) questions have been raised about the sensitivity of this large carbon store to climate change. Recent studies, mainly in British peatlands have suggested an increase in carbon export from peatlands driven by either an increased frequency of what some authors refer to as `biogeochemical drought' and/or increased productivity due to elevated CO$_{2}$. For the last six years we have continuously monitored the carbon input, outputs and change in storage in a northern peatland. The study site is the Mer Bleue bog of the Eastern Peatland Station in the Fluxnet Canada Research Network, located in the transition zone between the cool temperate and boreal ecoclimatic regions. We find net ecosystem production ranges from a sink of approximately 60 g m$^{-2}$ yr$^{-1}$ to a very small carbon source of less than 10 g m$^{-2}$ yr$^{-1}$ . Over the last six years, Mer Bleue has experienced most combinations of warm/cold, wet/dry growing and winter seasons. However, Mer Bleue in 2001 and 2002 was very dry (i.e. far in excess of what is term a 'biogeochemical' drought), as was much of northeastern North America. Even under these conditions Mer Bleue became only a small source of CO$_{2}$ and we saw no substantial increase in the mass loss of carbon as DOC. DOC is an important loss of carbon for the calculation of the net carbon balance since it can be equivalent to between 15 and 100% of the change in the annual carbon store, but DOC loss represents a fairly small mass flux of carbon (e.g. $<$ 10%) compared to the gross annual atmospheric inputs and output. Based on our calculations of the complete carbon balance we find no evidence for a large sustained increase in ecosystem respiration during prolonged dry periods which would be required for increased export of DOC. These results contrast with the hypothesis that increased `biogeochemical droughts' in British peatlands are driving the observed secular increase in DOC in rivers and streams over the last few decades.
DE: 1806 Chemistry of fresh water
DE: 1860 Runoff and streamflow
DE: 1615 Biogeochemical processes (4805)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting